Method for automatic scene balance of digital images

A scene balance correction method for a digital imaging device, comprising:

• a) determining a low-resolution image from an input image in an input color space;
• b) applying a color transformation to convert the low-resolution image to a standard color space to form a standard color space low-resolution image, wherein the standard color space has a defined set of RGB primaries that are selected so as not to cause any substantial color gamut limitations on the standard color space low-resolution image;
• c) analyzing the standard color space low-resolution image to determine a set of standard color space scene balance correction factors;
• d) determining a set of corresponding input color space scene balance correction factors from the standard color space scene balance correction factors using the color transformation;
• and
• e) applying the corresponding input color space scene balance correction factors to the input image to form a corrected input image, where the defined set of RGB primaries have CIE chromaticity values of x=0.8730, y=0.1440 for red, x=0.1750, y=0.9270 for green, and x=0.0850, y=0.0001 for blue.

A scene balance correction method for a digital imaging device, comprising the steps of:

• a) determining a low-resolution image from an input image in an input color space having a luminance channel and two color difference channels wherein the luminance channel and 2 color difference channels are computed from logarithms of color values in an RGB color space having a defined set of RGB primaries and the luminance and 2 color difference channels are computed using the following equations
• N=(RLog+GLog+BLog)/3
• GM=(2GLog−RLog−BLog)/4
• ILL=(BLog−RLog)/2
• RLog, GLog, and BLog being the logarithms of the color values in the RGB color space and wherein N is a luminance channel;
• GM is a color difference channel in a green magenta direction;
• and ILL is another color difference channel that is substantially aligned with the direction in which typical scene illuminants vary;
• b) applying a color transformation to convert the low-resolution image to a standard color space to form a standard color space low-resolution image;
• c) analyzing the standard color space low-resolution image to determine a set of standard color space scene balance correction factors;
• d) determining a set of corresponding input color space scene balance correction factors from the standard color space scene balance correction factors using the color transformation;
• and
• e) applying the corresponding input color space scene balance correction factors to the input image to form a corrected input image.

A computer program product comprising a computer readable storage medium having a computer program stored thereon for performing the steps of:

• a) determining a low-resolution image from an input image in an input color space;
• b) applying a color transformation to convert the low-resolution image to a standard color space to form a standard color space low-resolution image, wherein the standard color space has a defined set of additive RGB primaries having a matrix relationship to CIE XYZ tristimulus values and that are selected so as not to cause any substantial color gamut limitations on the standard color space low-resolution image;
• c) analyzing the standard color space low-resolution image to determine a set of standard color space scene balance correction factors;
• d) determining a set of corresponding input color space scene balance correction factors from the standard color space scene balance correction factors using the color transformation;
• and
• e) applying the corresponding input color space scene balance correction factors to the input image to form a corrected input image.

A scene balance correction method for a digital imaging device, comprising:

• a) producing a low-resolution image from an input image in an input color space where the low resolution image has a lower resolution that the input image;
• b) applying a color transformation to convert the low-resolution image to a standard additive color space to form a standard additive color space low-resolution image, the standard additive color space having additive primaries with no channel crosstalk;
• c) analyzing the standard color space low-resolution image to determine a set of standard color space scene balance correction factors;
• d) determining a set of corresponding input color space scene balance correction factors from the standard color space scene balance correction factors using the color transformation;
• and
• e) applying the corresponding input color space scene balance correction factors to the input image to form a corrected input image.